This invention relates to an improved multifrequency trunked, two-way radio communications system and, more particularly, to such a system wherein access to the system may be provided to a plurality of conventional, non-trunked, single channel radio units.
Trunked communications systems are well known in both the telephone and mobile radio communications art. In such systems, a plurality of subscribers share a predetermined number of transmission channels. The channels are assigned to subscribers by a trunked controller that can be implemented by a central control station or distributed control logic. The trunked controller truncates the channel assignment on the conclusion of an entire interchange message for message trunking or on the conclusion of a transmission for a transmission trunking. A transmission trunked communications system is described in U.S. Pat. No. 4,012,597 issued Nov. 24, 1975 to Lynk, Jr., et al., which is assigned to the same assignee as the present invention.
In a trunked communications system, each of the plurality of trunked mobile stations is specially equipped with control circuitry to enable requesting and receiving a channel assignment and to enable operating on the channel assigned by the trunked controller.
Trunked communications systems provide advantages over a conventional single channel system. System congestion problems of a single channel are avoided by a multichannel system. Additionally, the identifiable trunked stations and signaling capability thereof enable communications between selected ones of the trunked stations without alerting other trunked stations. However, when establishing a multifrequency trunked, two-way radio communications system, it is often not affordable to replace all the existing conventional, single channel units being used in an existing conventional communications system. Modification of the existing conventional single channel units to operate in a trunked system likewise would not be feasible.
There exists a need for an improved multifrequency trunked, two-way radio communications system in which a plurality of conventional, single channel radio units are provided access. Such access should enable two-way communications between the conventional, single channel radio units and the trunked mobile stations. Additionally, it is highly desirable that such access be provided without requiring burdensome manual operations at the plurality of conventional stations.